Co3O4 Nanosheets as Battery-Type Electrode for High-Energy Li-Ion Capacitors: A Sustained Li-Storage via Conversion Pathway.

We report the excellent charge storage performance of high-energy Li-ion capacitors (LIC) fabricated from the mesoporous Co3O4 nanosheets as the conversion-type battery component and Jack fruit (Artocarpus heterophyllus) derived activated carbon as a supercapacitor electrode, especially at high temperatures (50 and 40 °C). Prior to the fabrication, the electrochemical prelithiation strategy was applied to Co3O4 to alleviate the irreversibility and enrich the Li-ions for electrochemical reactions (Co0 + Li2O). The LIC delivered a maximum energy density of ∼118 Wh kg-1 at a high temperature of 50 °C. The significant difference is observed at a high rate of 2.6 kW kg-1 at 50 °C with excellent cycle stability up to 3000 cycles, with a retention of ∼87% compared with the LIC cycled at room temperature (∼74%). The magnificent electrochemical performance clearly demonstrates that the mesoporous structure and residual carbon synergistically facilitated the Li+/electron transport and hinder undesirable side reactions with electrolytes to realize high-energy density at high temperatures.

Practical Li-Ion Battery Assembly with One-Dimensional Active Materials.

Research activities on the development of one-dimensional (1D) nanostructures and their successful implementation in the fabrication of high-performance practical Li-ion batteries (LIBs) are described. Although numerous 1D-structured materials have been explored for use in LIBs as anodes, cathodes, and separator-cum-electrolytes, only a very limited number of studies report the practical assembly of LIBs using these components. As a result, the salient features of using 1D materials in charge-storage devices have not been realized from an application perspective. Exceptional battery performance is reported when all-1D-based electro-active materials are used to fabricate LIBs. Using all-1D nanostructures not only provides high power capability, energy density, and durability, it also opens up new avenues for developing high-performance next-generation Li-ion power packs.

Biomass-Derived Electrode for Next Generation Lithium-Ion Capacitors.

We report the fabrication of a carbon-based high energy density Li-ion hybrid electrochemical capacitor (Li-HEC) from low cost and eco-friendly materials. High surface area (2448±20 m(2) g(-1) ) activated carbon (AC) is derived from the environmentally threatening plant, Prosopis juliflora, and used as the positive electrode in a Li-HEC assembly. Natural graphite is employed as negative electrode and electrochemically pre-lithiated prior to the Li-HEC fabrication. The Li-HEC delivers a specific energy of 162.3 Wh kg(-1) and exhibits excellent cyclability (i.e., ∼79 % of initial capacity is retained after 7000 cycles). The superior electrochemical performance of Li-HEC benefits from the tube-like unique structural features of the AC. Also, the presence of a graphitic nanocarbon network improves the ion transport, and the formed micro- and meso-porous network acts as reservoir for the accommodation of charge carriers.

Synthesis of 2D/2D Structured Mesoporous Co3O4 Nanosheet/N-Doped Reduced Graphene Oxide Composites as a Highly Stable Negative Electrode for Lithium Battery Applications.

Mesoporous Co3O4 nanosheets (Co3 O4 -NS) and nitrogen-doped reduced graphene oxide (N-rGO) are synthesized by a facile hydrothermal approach, and the N-rGO/Co3O4 -NS composite is formulated through an infiltration procedure. Eventually, the obtained composites are subjected to various characterization techniques, such as XRD, Raman spectroscopy, surface area analysis, X-ray photoelectron spectroscopy (XPS), and TEM. The lithium-storage properties of N-rGO/Co3O4 -NS composites are evaluated in a half-cell assembly to ascertain their suitability as a negative electrode for lithium-ion battery applications. The 2D/2D nanostructured mesoporous N-rGO/Co3O4 -NS composite delivered a reversible capacity of about 1305 and 1501 mAh g(-1) at a current density of 80 mA g(-1) for the 1st and 50th cycles, respectively. Furthermore, excellent cyclability, rate capability, and capacity retention characteristics are noted for the N-rGO/Co3O4 -NS composite. This improved performance is mainly related to the existence of mesoporosity and a sheet-like 2D hierarchical morphology, which translates into extra space for lithium storage and a reduced electron pathway. Also, the presence of N-rGO and carbon shells in Co3O4 -NS should not be excluded from such exceptional performance, which serves as a reliable conductive channel for electrons and act as synergistically to accommodate volume expansion upon redox reactions. Ex-situ TEM, impedance spectroscopy, and XPS, are also conducted to corroborate the significance of the 2D morphology towards sustained lithium storage.